Marine weather

Weather conditions can make the difference between an enjoyable day out and a dangerous, perhaps tragic trip. Remember that the weather can change suddenly and without warning.

Make sure you always use a marine weather forecast. Land and general forecasts do not take in to account wind speed over water, which is double that over the land, or the size of waves.

Marine forecasts are almost always accurate when predicting major weather events, such as gales. They can be less accurate when predicting local changes of conditions, so you should always be prepared for the unexpected 

Parts of marine forecasts

Warnings

These are issued for gales or storms anywhere on the New Zealand coast. A wind warning may be included in local area forecasts if wind gusts are expected to reach 33 knots (about 60 km/hr). 

Situation

A description of the position and movements of highs, lows and frontal systems expected to affect the New Zealand coast within the next 36 hours. It also names those areas affected by warnings.

Areas

The Recreational Marine Forecast covers most boating areas. Details of the current wind strength can be heard on VHF Radio.

Forecast details

A description covering the next 24 hours of expected average conditions over open water.

Wind: direction, such as northwest, is the direction the wind is expected to come from. Speed is given in knots, and one knot is approximately 2 kilometres an hour. This is an average speed so always expect that gusts may be 50% higher. Also allow for funnelling between headlands causing the wind speed to double.

Sea: a description of the waves formed by the local wind.

Swell: caused by longer waves that come from the ocean. Swells increase in height when they reach shallow water.

Visibility: given when visibility is expected to be less than six miles (10 kilometres).

Outlook: all marine forecasts are for up to 48 hours with the outlook for a further 3 days.

Wind and tide: When the wind is opposing the tide, expect a much rougher sea. When the wind is with the tide, expect a calmer sea.

Sources of marine weather

The two most convenient marine weather sources are VHF radio and metphone.

Maritime NZ Maritime Radio provides VHF radio forecasts which are announced on Channel 16 at 0533, 0733, 1033, 1333, 1733 and 2133 hours.

Other sources of marine forecasts include:

  • The MetService Marine smartphone app
  • local Coastguard stations on VHF radio
  • www.metservice.co.nz [New Zealand’s national meteorological service]
  • private coastal radio stations and radio stations for fishermen
  • local newspapers – but remember they can be published many hours earlier and are often out of date
  • local radio stations, especially in summer
  • on National Radio at 0400 hours.

For more information check out Maritime NZ's Marine Weather Forecasts page